In the UK at least, full RCD protection for all domestic circuits was only mandated by the 18th edition of the wiring regs. They came into force in January 2019

In the UK at least, full RCD protection for all domestic circuits was only mandated by the 18th edition of the wiring regs. They came into force in January 2019. Before that, it was typical to install split consumer units in which the sockets were RCD protected but the lighting circuits, smoke detectors etc were not. Even now, circuits in commercial settings can be installed without RCDs. Unfortunately then, there are still quite a lot of recent circuits out there that don't have full protection. Which is a shame because RCDs are excellent.